This invention relates to a poppet valve in which a pilot spool is used for controlling a poppet, and the flow of a pressurized fluid is thereby controlled.
In an ordinary construction of the poppet valve, since the pilot spool is provided to extend outside through a chamber formed on the rear side of the poppet, the cross-sectional area of the rearward end of the poppet in the chamber is smaller than the cross-sectional area of the forward end of the poppet, to which the pressurized fluid supplied to the poppet valve is directly applied. As a consequence, an additional device such as a spring must be provided in the chamber for augmenting the pressure of one part of the pressurized fluid introduced in the chamber when the poppet is to be retracted for interrupting the flow of the pressurized liquid. However, the provision of the spring not only complicates the construction of the poppet valve, but also entails various difficulties such that the spring force must be changed in accordance with the variation of the pressure of the pressurized fluid and design of the spring becomes difficult when the stroke of the poppet is large. For obviating the above described difficulties, a construction utilizing a separate control liquid of a higher pressure than that of the controlled fluid has been proposed. However, such a construction exhibits a difficulty of further complicating the poppet valve.